A W=1 build of 44x/iss476-smp_defconfig gives:

arch/powerpc/mm/nohash/44x.c:220:13: error: no previous prototype for 'mmu_init_secondary' [-Werror=missing-prototypes]
  220 | void __init mmu_init_secondary(int cpu)
      |             ^~~~~~~~~~~~~~~~~~

That function is called from head_4xx.S

Add a prototype in mmu_decl.h

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Arnd Bergmann <arnd@arndb.de>
---
 arch/powerpc/mm/mmu_decl.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index c6dccb4f06dc..7f9ff0640124 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -110,6 +110,7 @@ extern void MMU_init_hw(void);
 void MMU_init_hw_patch(void);
 unsigned long mmu_mapin_ram(unsigned long base, unsigned long top);
 #endif
+void mmu_init_secondary(int cpu);
 
 #ifdef CONFIG_PPC_E500
 extern unsigned long map_mem_in_cams(unsigned long ram, int max_cam_idx,
-- 
2.41.0

On Thu, 17 Aug 2023 16:25:49 +0200, Christophe Leroy wrote:
> A W=1 build of 44x/iss476-smp_defconfig gives:
> 
> arch/powerpc/mm/nohash/44x.c:220:13: error: no previous prototype for 'mmu_init_secondary' [-Werror=missing-prototypes]
>   220 | void __init mmu_init_secondary(int cpu)
>       |             ^~~~~~~~~~~~~~~~~~
> 
> That function is called from head_4xx.S
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/47x: Add prototype for mmu_init_secondary()
      https://git.kernel.org/powerpc/c/b27c1a0a4e62af1fd9d2688bf8156a5d546e4227

cheers